Ecological correlates of alternative reproductive tactics

Submitted by Michi on 3 June 2024.

Susan McRae measuring American moorhen eggs in Panama. Photo: Marco Guerra

Text by Susan McRae

Hannu Pöysä’s long-term study on ecological factors affecting rates of conspecific brood parasitism (CBP) in goldeneyes in Finland was published in Journal of Avian Biology in March this year. His article insightfully highlights the effects of climate-change induced variation in season length on CBP. This adds to his earlier work emphasizing the effects of nest predation risk on rates of CBP. Emprirical data from the long-term study inspired the Pöysä and Pesonen (2007) model relating levels of brood parasitism to nest predation risk, an important advance in our understanding of the assessment of risk at the local level by laying females.

Here's the backstory of how I came to be interested in this topic. When rats raided many of my common moorhen nests during the last season of my PhD, I was devastated! I thought that it would greatly diminish my thesis. On the contrary, it provided for an additional chapter, one I had not planned for. After a few weeks of observation, it was crystal clear that the CBP rate was positively related to the nest predation rate. I often tell this story to my students to inspire them to go where the research takes them. I published my paper on this in Journal of Animal Ecology, but it received relatively little attention.

                 Common moorhen (Gallinula chloropus). Photo: Tisha Mukherjee, Wikimedia Commons.

                         Parasitized common moorhen nest with eggs laid out, host on top row, parasitic in bottom row. Photos: Susan McRae

I might have stayed in Cambridge to study that population of common moorhens long-term. However, as fate would have it, with the Wildfowl and Wetlands Trust having decided to cease their management of Peakirk Waterfowl Gardens where my study took place, it became untenable to work there. The new management eventually closed it down (this was a terrible loss for scientific outreach in the community and informal education for the schoolchildren of the Peterborough region!).

I was fortunate to conduct postdoctoral work in Namibia and then in Panama on different species of moorhens. I was amazed to see not only higher rates of parasitism in these wilder settings, but also more sophisticated responses by hosts in these populations. I learned that it really pays to go out and study different systems. Alas, have been constrained to staying put for most of the rest of my career, though I don’t regret moving more into conservation. I would have loved to have spent my academic career studying moorhens in wetlands around the world!

My Viewpoint article in Journal of Avian Biology emphasizes the importance of both long-term studies and comparing similar populations with different ecology. There are relatively few other studies that have really explored the relationship between CBP and nest predation in a quantitative manner. Let's hope that changes.

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